rGad c 1, Cod

Further Reading

Cod f3

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Code: f426
Latin name: Gadus morhua
Source material: rGad c 1 is a CCD-free recombinant protein

Possible clinical utility

Parvalbumin is reported as the major allergen in fish. Due to the high degree of cross-reaction between parvalbumin from different fish species, rGad c 1 could be a valuable tool when diagnosing patients with fish allergy.

Allergen description

The Atlantic cod, Gadus morhua, is a well-known food fish belonging to the family Gadidae. Its fast, white ‘twitching’ muscle contains parvalbumins, which are calcium-binding proteins generally found in lower and higher vertebrate muscle. Gad c 1 is a 12.3 kDa parvalbumin and a major cod allergen. Cod Gad c 1 was the first fish allergen isolated as a pure fraction and it has since served as a marker for fish allergy. As an allergen, Gad c 1 is very stable; its allergenic activity is dependent on the amino acid sequence and not necessarily on its steric configuration. (1)

Clinical experience

Fish, especially cod, is a common cause of food allergy and atopic dermatitis, particularly in countries of the Northern Hemisphere (2-7)and in Asia. Contact with cod via ingestion or inhalation of cooking vapours has resulted in allergic symptoms, including oral allergy syndrome, generalised urticaria, facial angioedema and anaphylaxis. (9-11) Wheezing and life-threatening bronchospasm have been reported. (12) Contact with fresh raw cod has also resulted in allergic dermatitis, urticaria and anaphylaxis. (13-15) Immediate allergic reactions may follow ingestion of even minute amounts of cod. (16)

Patients allergic to fish often have dramatic symptoms, and severe asthmatic attacks can be triggered just by the smell of fish, for example. Extremely sensitive patients have suffered anaphylactic shock after eating foods cooked in reused cooking oil tainted with fish, or when utensils and containers have been used earlier for cooking fish. (17-18)

Potential cross-reactivity

Carp parvalbumin, Cyp c 1, has been shown to contain 70% of the IgE epitopes present in natural extract of cod, tuna and salmon (Sal s 1). (19-20) Other studies have also reported the presence and cross-reactivity of parvalbumins from different fish species (cod, tuna, salmon, perch, carp and eel). (21)

Parvalbumin in carp and cod has been shown to be cross-reactive, and cod Gad c 1 (or carp Cyp c 1) could therefore be utilised for the diagnosis of fish allergy. Some fish-hypersensitive patients can tolerate certain fish species while being allergic to others. If a parvalbumin allergen is involved, however, cross-reactivity between fish species is a strong possibility. For example, a study that evaluated cross-reactivity among 9 common edible fish – cod, salmon, pollack, mackerel, tuna, herring, wolffish, halibut and flounder – using sera from 10 fish-allergic patients showed that cod (Gad c 1), salmon (Sal s 1), pollack (The c 1), herring and wolffish shared antigenic and allergenic determinants. In contrast, halibut, flounder, tuna and mackerel displayed the lowest cross-reactivities.


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  18. Yunginger JW, Sweeney KG, Sturner WQ, Giannandrea LA, Teigland JD, Bray M, Benson PA, York JA, Biedrzycki L, Squillace DL, et al. Fatal food-induced anaphylaxis. JAMA 1988;260(10):1450-2.
  19. Torres Borrego J, Martinez Cuevas JF, Tejero Garcia J. Cross reactivity between fish and shellfish. [Spanish] Allergol Immunopathol (Madr) 2003;31(3):146-51
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  21. Lindstrom CD, van Do T, et al. Cloning of two distinct cDNAs encoding parvalbumin, the major allergen of Atlantic salmon (Salmo salar). Scand J Immunol 1996;44(4):335-44


As in all diagnostic testing, the diagnosis is made by the physican based on both test results and the patient history.